This invention relates to an excavating tooth and, more particularly, to an excavating tooth having a unique connection between the point and adapter. As such, the invention relates to two-part teeth. At about the turn of the century, workers in the excavating art saw the merit of providing replaceable tips, viz., "points" on the tooth shank or adapter, so as to renew the penetrating portion without expensive down-time--see, for example, U.S. Pat. No. 564,664.
A conventional way of temporarily locking the point on the adapter was to use a pin lock extending through aligned openings in the point and adapter nose.
According to the instant invention, a significant improvement has been made in the excavating tooth art by the use of a lock external to the coupling. An immediate advantage accuring from this arrangement is that the adapter nose can be solid, i.e., the heretofore commonplace locking pin opening is eliminated. It is in the area of the pin opening that most nose failures occur--so that art workers have had to "beef-up" this portion of the nose. Normally, the lock opening is positioned near the shoulder which joins the nose to the relatively massive adapter shank so that this has been an additional concern--providing an area of weakness immediately adjacent an area of transition, classically an area of incipient failure in itself. However, the wedge or tapered shape of the nose--dictated by the need for easy assembly and proper performance--also dictated that the pin opening be as rearward as possible so as to be in the section of greatest area, hence, strength. But, as pointed out just above, this intruded on the classically weak area of transition and aggravated the weakness.
However, by utilizing a solid nose as the coupling means with the lock external thereto, the adapter is strengthened to such an extent that, according to the preliminary tests, the rupture resistance of the nose in the inventive tooth is that of a conventional tooth one or two sizes larger, i.e., 20% stronger than the comparable prior art tooth of the same size. For example, teeth are generally sized according to the horizontal dimension across the rear of the point, expressed in inches--so the inventive tooth has the strength of a conventional tooth 1/2"-2" wider.
The provision of the external lock provides a second and equally desirable advantage--the shear forces normally applied to the locking pin are converted to compressive forces so that a much smaller pin is used, again resulting in better use of the available metal in the tooth. It will be appreciated that in past teeth an impact tending to remove the point resulted in shearing forces at the ends of the centrally-located locking pin. In other words, the movement of the inside of the point relative to the outside of the nose tended to shear the pin in the plane of movement. However, with the inventive arrangement, any movement of the point in a twisting, sideways or up and down fashion applies the nominally shearing forces at points where the locking pin is bolstered against a portion of the adapter--so that what ordinarily would be a shearing force is converted to a compressive force. Thus, the force that in conventional teeth would tend to transversely sever the metal now tends to elongate the same--against which the metal has much greater resistance. It should be appreciated that the unseating forces come from all angles and therefore normally have a sideways component.
Historically, locking pins have extended vertically through the point and adapter nose so as to facilitate disassembly. Horizontal pins have been used but have uniformly been considered "knuckle-busters" because of the difficulty of access. This impedes one principal function of the lock--to be easily removable so as to permit quick replacement of the point. The other principal function is, of course, to keep the point firmly mounted on the adapter against inadvertent removal.
The invention achieves the beneficial results of the vertical pin locks of the past by using rearwardly extending tongues on the point sides to provide the means adapted to receiving vertical pins--so that at the same time the lock is not only lateral and rearward of the coupling section but also able to receive a vertical pin. Even further, the provision of the tongues reduces further the stress to be resisted--by at least 1/2--because two locks are available without sacrificing valuable wear metal.
Although rearwardly extending tongues on points have long been used--see U.S. Pat. No. 2,483,032--they have not been used so far as is known to the inventors hereof for locking, rather only for secondary stabilization. In fact, the only disclosures known to the inventors hereof using an external lock are U.S. Pat. No. 2,666,272 and German Pat. No. 390,476. These, and co-owned U.S. Pat. No. 3,496,658, none of which was employed commercially so far as known, are the only teachings where the aligned vertical lock openings were eliminated from the nose and point.
In the preferred form of the invention, an inverted U-shaped locking pin is employed which straddles the adapter and engages slots in the rearwardly extending tongues--thereby simultaneously achieving greater nose strength and the advantageous vertical removal. Additionally, the bight portion of the U-shaped pin is received within a transverse recess in the adapter top to protect the pin while providing means for such removal--and also while being located in the massive section of the adapter so as not to intrude into the areas of potential failure described above.
In the instance where a heavy impact load is concentrated near the tip of the tooth, it is advantageous to provide additional means for secondary stabilization generally following the principle of U.S. Pat. No. 3,079,710. The structures used previously to provide such stabilization, viz., "flats" on the nose and socked have been made much more useful per se in the inventive tooth. This has been achieved through extending nearly square-sided rails out to the tip of the nose of the adapter and apex of the point socket while positioning them at the corners of the nose and socket apices.
These terminal portions of the rail means have been found to be advantageous cooperating with the "flate" of the stabilized nose and socket to prevent "peeling" of the point from the adapter upon the application of concentrated impact loads by developing more stabilized bearing surfaces all the way along the length of the nose and socket.
In the preferred embodiment the rib or rail means are nearly square-sided and non-uniform in cross-section along their length--being larger adjacent the nose or socket tips or apices as they are nearly circumscribable (less draft) inside a cylinder but are reduced in size toward the rear due to inscribed conical nose in the illustrated embodiment.
Other advantages, both general and specific, of the invention can be appreciated as this specification procees.